[turbofan] Add a mutex for recording compilation statistics

src/compilation-statistics.h

Index: src/compilation-statistics.h
diff --git a/src/compilation-statistics.h b/src/compilation-statistics.h
index ceffc2ebc19fcebc297d96e7aba4a63468abcdb9..388117b10ed30083b37bff9cac59fe8d3546eb56 100644
--- a/src/compilation-statistics.h
+++ b/src/compilation-statistics.h
@@ -80,6 +80,7 @@ class CompilationStatistics final : public Malloced {
   TotalStats total_stats_;
   PhaseKindMap phase_kind_map_;
   PhaseMap phase_map_;
+  base::Mutex record_mutex_;
 
   DISALLOW_COPY_AND_ASSIGN(CompilationStatistics);
 };